Thermostatic switch



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April 27, 1937. D. EISING'A THERMOSTATIC SWITCH Filed Nov. 14, 1954April 27, 1937. D EislNGA 2,078,531

THERMOSTATIC SWITCH Filed Nov. 14, 1954 2 Sheets-Sheet 2 Ik 15J nya AITORNEY @WMM Patented Apr. 27, 1937 UNITED STATES 'rHERMosTATIc swrtrcnDirk Eisinga, Glendale, Calif., assignor to National Steel ConstructionCo., Seattle, Wash., a corporation of Washington Application November14, 1934, Serial No. 752,964

6 Claims.

My invention relates to thermostatic switches and the general object ofmy invention is to provide a thermostatic switch of simple and eicientconstruction which is especially well adapted for use in connection withliquid containers in which the thermostatic element may be immersed inthe liquid.

An important object of the invention is to provide a thermostatembodying a tube of metal 10 having a high coeiiicient of expansion,which tube serves as a thermostat element and at the same time serves asa housing for other thermostat mechanism including a metal rod having alow coeiiicient of expansion and adapted to cooperate with said metaltube.

Another important object of the invention is to provide a thermostatswitch of this nature which is provided with simple and eicient quickmake and quick break means for opening and closing the switch with asnappy movement.

A further object of the invention is to provide a thermostatic switch ofthis type in which all ofthe operating mechanism is readily removablefrom the housing in which it is contained without removing said housingfrom the liquid container or tank in which it is installed.

A still further'object is to provide a thermostatic switch which employsa relatively strong tension spring for moving electrical contact memberswith a snappy movement back and forth between open switch and closedswitch positions, and, in which the parts cooperating with this springare arranged so that the deflection of said parts duento the tension ofthis spring is substantially negligible.

Another object is to provide a thermostatic switch employing a spring,as above set forth, in which the spring may be assembled with the leversand other parts while there is no tension on said spring and in whichtension may be placed on .said spring, after assembly, by the turning ofan adjusting screw by which the thermostat is adjusted.

Another object of the invention is to provide a thermostatic switch inwhich the thermostat is readily adjustable to operate at variousdifferent temperatures.

When thermostatically controlled switches of this nature are installedin connection with hot Water tanks they are diflicult to remove from thetanks and require the draining of the tanks previous to their removal.My invention makes it unnecessary to remove the housing of thethermostatic switch from the tank for repair because all of theoperating mechanism is accessible from the exterior without removing thethermostatic switch housing.

Other and more specific objects of the invention will be apparent fromthe following description taken in connection with the accompanying 5drawings.

In the drawings Fig. 1 is a longitudinal sectional view of athermostatic switch constructed in accordance with my invention showingthe same in closed switch position. 10

Fig. 2 is a similar view showing the switch in open position.

vle"ig..3 is a cross sectional view substantially on broken line 3 3 ofFig. 2, parts being shown in elevation.

Fig. 4 is a sectionalview substantially on broken line 4 4 of Fig. 1.

Fig. 5 is' a detached plan view of a switch lever showing contact means,a spring and a fragment of a lever arm connected therewith. 20

Fig. 6 is a fragmentary sectional view on an enlarged scale of the endof a thrust rod and a cooperating adjusting screw.

Fig. 7 is an elevation, on a reduced scale, with parts broken away,illustrating an installation of this invention in connection with a hotliquid storage tank.

Like reference numerals designate like parts throughout the severalviews.

Inthe drawings I0 designates a tube formed 30 of metal having a highcoeicient of expansion.

I prefer to make this tube of copper although obviously other metals ormetal alloys may be used. The tube I0 is closed at one end as by a capII and has its other end connected with a 35 housing I2, preferably bythreading the end of the tube into said housing. The threaded jointsbetween the cap I I, tube I0 and housing I2 are preferably furthersealed by externally soldering the same, as at I3, thus precluding anypossi- 40 bility of leakage of water or other liquid past these joints.The housing I2 is larger than the tube I0 to aiord room for theinstallation of switch mechanism and said housing I2 is externallythreaded, as at I4 so that it may be screwed 45 into the side of aliquid container I5. The portion I6 of the housing in which the switchmechanism is contained may be of generally rectangular shape, as shownin Fig. 3.

The thermostatic mechanism which cooperates 5C with the tube I0 inproviding the movement for operating the electric switch is in thenature of a, metal rod I1 having a low coefficient of expansion and alever arm I8, cooperating with said rod I'I and with the tube IIl, whichhas a high coefilcient of expansion. The rod I1 has a hardened bearingmember 28 on one end thereof. The bearing member 28 has a knife edge 2Iwhich bears against a recessed and hardened yseat 22 in an angularportion 23 of the end of the lever arm I8. The tip 24 of the angularportion 23 rests against a hardened bearing disc 25 which is supportedby the cap Il. This provides a. relatively short lever arm 23 betweenthe tip 24 and bearing seat 22 and a relatively long lever arm from thebearing seat 22 to the other end of the lever I8. The rod I1 and leverI8 both extend throughout substantially the entire length of the tube I8and have their rear end portions positioned in the housing I2. Theforward end portions of the rod I1 and lever I8 are loosely connectedtogether to prevent sidewise displacement thereof by a dowel pin I8which is rigid with the bar I1 and ilts loosely into a hole 29 in thelever I8. The pin I8 has a length only slightly less than the diameterof the tube I8 and serves as a means for preventing movement of the endportion of rod I1 transversely of the tube.

The end portion of the rod I1 which is positioned in the housing I2 tsslidably within a tubular boss 26 which is rigid with an end plate 21.'I'he end plate 21 is removably secured to the end of the housing I2 asby screws 28. A flattened cross pin 38, in the end portion of the rod 21which fits into the tubular boss 26, is positioned within longitudinalslots 3I in said tubular boss 26. This cross pin 38 serves as a guidingmeans for the rod I1 and prevents the same from turning. A hardenedsteel ball 32, see Fig. 6, is provided in the end of the rod I1 forengagement by a hardened concave bearing member 33 on the end of a screw34 which is threaded into the tubular boss 28. The head of the screw 34is positioned on the exterior of the end plate 21 and is provided with arigidly connected cross arm 35 which serves both as a iinger piece bywhich the screw may be turned and as a pointer for indicating thesetting of said screw. The end plate 21 may have suitable spaced apartgraduations 38 thereon, to which the cross arm 35 may be set. It will beapparent that a relatively slight longitudinal movement of rod I1produced by turning of screw 34 will produce a much greater movement ofthe movable end portion of lever arm I8, which is positioned withinhousing I2, the screw 34 thus serving as a ready means for adjusting theswitch to operate at different temperatures.

The end portion of the lever arm I8 which is positioned in the housingI2 is preferably offset upwardly for purposes of clearance and isconnected with one end of a tension spring- 31. The other end of thetension spring 31 is connected with a plate portion 38 of a switchlever. This switch lever has two spaced apart arms 48 between which thespring 31 is operatively disposed. The ends of the arms 48 remote fromthe plate 38 are provided with knife edge bearings 4I which seat withinV shaped notches 42, see Fig. 2, in a washer 43. The washer 43 restsagainst a suitable shoulder 44 which is formed within the housing I2 atsubstantially the location of the end o f the pipe I8 and said washermay also rest against the end of the pipe I8 as shown in Figs. 1 and 2.A dowel pin 45 in washer 43 is adapted to t within a. suitable hole 48in the shoulder 44 to angularly position the washer 43 so that the Vshaped notches 42 will be maintained in the correct location to receiveand hold the knife edge bearings 4I of the switch lever.

'I'he tension spring 31 exerts a pull on the plate 38. This places thearm members 48 under compression and presses the knife edges 4I againstthe washer 43. If the line of pull of the spring 31 coincides with theplane of the switch lever, that is, with the plane which passes throughthe fulcrum point 4I-42 and through a point 41 from which the pull ofthe spring is exerted on the plate 38, then there will not be anytendency for the switch lever to pivot or swing in either direction. Ifthe line of pull of the spring is shifted to either side of the abovementioned plane, then a component of the force exerted by the spring 31will tend to angularly move the switch lever 38-48 in a. directiontoward the side of the plane of the switch lever to which the pull isexerted. It is thus apparent that by moving the end of the lever arm I8to which the spring 31 is connected it is possible to shift the line ofpull of the spring 31 to either side of the plane passing through points41 and 4I-42 and thus move the switch lever with a quick snappy movementin either direction. The movable end of the lever arm I8 is moved byexpansion and contraction of the tube I8.

As the pull of the spring 31 is exerted substantially longitudinally ofthe switch lever 48- 38 and lever arm I8, at all times, and is notexerted directly on other levers or parts, the tendency of said springto deflect parts is substantially negligible.

A support 48 of insulating material mounted on the switch plate 38carries an electrical contact member 58. This contact member 58 projectsabove the support 48 and is adapted to make electrical contact withanother contact member 5I which is carried by a cover plate 52 of insu'-lating material. The cover plate 52 is secured to the housing I2 as byscrews 53, and also serves as a closure member for the top of saidhousing. The contact member 5I has a binding post portion 54 whichextends upwardly through the cover plate 52 and is electricallyconnected with a terminal clip 55 to which any suitable circuit wire maybe electrically connected. A flexible electrical conductor member 56,see Fig. 3, connects the contact member 58 with another terminal clip 51on the cover plate ,52, thus affording means for closing an electricalcircuit between terminal clips 55 and 51 when electrical contact members58 and 5I are in electrical contact with each other. As conductor member58 is very flexible and of substantial length it will not retard orhamper the free movement of the switch lever. A bolt 58 and nut 58 maybe used to connect conductor member 56 with terminal clip 51 as shown inFig. 3.

'Ihe amount of angular movement of the switch lever in the directionrequired to close the switch is limited by engagement of the two contactmembers 58 and 5I, while angular movement of said switch lever in thedirection required to open the switch may be limited by engagement ofthe plate member 38 with two shelf like portions 88 of the housing I2,or may be limited by engagement of an adjustable screw 62 in the plate38 with the top of the boss 28, said screw affording a means ofadjusting the throw of the switch lever in one direction.

In dis-assembling this device the screw 34 is first retracted far enoughto relieve tension on the spring 31. The end plate 21 is then removedcarrying the screw 34 with it and leaving the rod I1 and all of theother parts in the tube I8 and housing I2. The nut 59 which secures theilexible conductor to the terminal clip 51 is then removed leaving saidflexible conductor free and unattached as respects the housing. I'he rodI1, lever I8 and switch plate 38, together with all of the partsattached thereto may then be freely withdrawn from the tube I0 andhousing I2.

In assembling the device the rod I1, lever I8, switch plate 38 and partsconnected therewith including the spring 31 are first connected togetherin the proper way and are then inserted in the housing I2 and tube I0.The nut 59 is then placed on the bolt 58 to electrically connect theflexible conductor to the terminal clip 51. After this has been doneYthe several parts will all be in their proper relation but the spring 31will not be under tension and the tip 24 of the lever I8 will not bepressed against the disc 25. The end plate 21 is then put in place andsecured to the housing I2 with the adjusting screw 34 retracted. Thisscrew 34 is then screwed inwardly forcing the rod I1 toward the cappedend of the tube I0 and placing the spring 31 under tension. After thetip 24 of the portion 23 of lever arm I8 has engaged the disc 25 therear end of said lever arm will be moved upwardly into a position asshown in Fig. 1, and the switch contact 50 will be snapped from an opento a closed position as respects switch contact 5I. 'I'he finger piece35 may then be set, by reference to the graduations 36 so that theswitch will operate at approximately the desired temperature, and thisadjustment may be varied, after observing the actual operation of thedevice, to secure opening and closing of the switch at the exacttemperatures desired. This thermostatic switch may be installed in theside of a liquid container I5 in close proximity to an electric fluidheater 6I as indicated in Fig. 7, and adjusted to operate at any desiredtemperatures. When the temperature of the fiuid surrounding the tube I8is below the predetermined minimum, at which the thermostat is adjustedto operate, the longitudinal contraction of the tube I0 will press thedisc 25 against the tip of the lever arm I8 hard enough to angularlymove said lever arm I8 about the fulcrum formed by knife edge ZI thusmoving the rear end of said lever arm I8 away from the rod I1. Thisshifts the line of pull of the spring above the plane of the switchlever 38-40 and causes the contact member 5I! to be moved intoelectrical engagement with the contact member 5I thus closing anelectrical circuit to the fluid heater 62 and putting said heater intooperation. As the temperature of the liquid in the tank surrounding thethermostat tube I0 increases the tube I0 will expand longitudinallywhile the length of the rod Il will remain substantially constant. Thiswill allow the free end of the lever arm I8 to move downwardly bygravity and when the line of pull of the spring 31 has moved below aline which passes through the points 4I and 41 the switch will besnapped to open position and the circuit controlled by said switchbroken. The breaking of this circuit with a quick snappy movementprevents damage to contact members 58 and 5I by arcing. 'I'he thermostatis always installed with the tube I il in a generally horizontalposition and the lever I8 above the rod I1. The end portion of the leverI8 is heavy enough so that it will always tend to drop by gravity intothe open switch position shown in Fig. 2 unless it is urged into anelevated position as shown in Fig. 2, by

pressure exerted at the locations 2| and 22 on the shorter arm 23 ofsaid lever I8.

The foregoing description and accompanying drawings clearly disclose apreferred embodiment of my invention but it will be understood that thisdisclosure is merely illustrative and that such changes in the inventionmay be 'made as are fairly within the scope and spirit of the followingclaims.

I claim:

1. In a thermostatic apparatus, a tube; a rod member disposedlongitudinally within said tube, said rod member having a lowercoefcient of expansion than said tube; a housing rigid with one endportion of said tube; means rigid relative to said housing supportingone end of said rod member; movable lever means' positionedlongitudinally within said tube having one end extending into saidhousing; a relatively short rigid inclined arm member on the end of saidlever means remote from said housing; a knife edge bearing on the outerend of said rod engaging said short arm member adjacent the junction ofthe same with said lever means; means rigid with the outer end portionof said tube engaging the end of said short lever arm member; andcircuit opening and closing means positioned in said housing operativelyconnected with the end portion of said lever means.

2. In a thermostatic apparatus, a tube; a rod member disposedlongitudinally within said tube, said rod member having a lowercoefficient of expansion than said tube; a housing rigid with one endportion lof said tube; an adjusting screw threaded in said housingoperable from the exterior of the housing and providing an adjustablethrust support for one end of said rod; movable lever means positionedlongitudinally within said tube having one end extending into saidhousing; a relatively short rigid inclined arm member on the end of saidlever means remote from said housing; a knife edge bearing on the outerend of said rod engaging said short arm member adjacent the junction ofthe same with said lever means; means rigid with the outer end portionof said tube engaging the end of said short lever arm member; andcircuit opening and closing means positioned in said housing operativelyconnected with the end of said lever means.

3. In thermostatic apparatus; a tube having one closed end; a housingrigidly secured to the other end of said tube; a rod member disposedlongitudinally within said tube and extending into said housing, saidrod member having a different coeiicient of expansion than said tube;adjustable means rigid relative to said housing providing a thrustsupport for one end of said rod member; a movable lever member extendinglengthwise within said tube, said lever having means positioned betweenthe end of said rod and the closed end of said tube for moving saidlever in response to relative differences in the lengths of said tubeand said rod produced byvariations of temperature; a switch leverpositioned in prolongation of said lever member and fulcrumed adjacentthe end of said lever member; a tension spring connecting the movableend portion of said lever member with the movable end portion of saidswitch lever, the vend of said lever member which is connected with saidspring being movable back and forth across a straight line which passesthrough the'fulcrum of said switch lever and the point of connection ofsaid spring with said switch lever, whereby said switch lever` will bemoved back and forth with a quick movement; and circuit opening andclosing means carried by said switch lever.

4. In thermostatic apparatus, a tube having one closed end; a housingrigidly secured to the other end of said tube; a rod member disposed'longitudinally within said tube and extending into said housing, saidrod member having a different coeiiicient of expansion than said tube;adjustable screw means in said housing providing a thrust support forone end of said rod; movable lever means positioned longitudinallywithin said tube having one end extending into said housing; arelatively short rigid inclined arm member on the end of said levermeans remote from said housing; a knife edge bearing on the outer end ofsaid rod engaging said short arm member adjacent the junction of thesame with said lever means; means rigid with the closed outer endportion of said tube engaging the end of said short lever arm member; aswitch lever positioned in prolongation of said lever member andfulcrumed adjacent the end of said lever member; a tension springconnecting the movable end portion of said lever member with the movableend portion of said switch lever, the end of said lever member which isconnected with said spring being movable back and forth across astraight line which passes through the fulcrum of said switch lever andthe point of connection of said spring with said switch lever, wherebysaid switch lever will be moved back and forth with a quick movement,said adjusting screw supporting the end of said rod member serving toplace said spring under tension after said thermostat mechanism isassembled; and circuit opening and closing means carried by said switchlever.

5. In thermostatic apparatus, a tube; a housing rigidly connected withone end of said tube; a tubular boss in said housing having guide meanstherein; a rod extending lengthwise of said tube and into said housing,the end portion of said rod being positioned in said tubular boss; crosspin means in the rod operable in said guide means supporting said rodagainst rotation; a lever arm positioned lengthwise within said tubeabove said rod; dowel pin means loosely connecting said rod and saidlever arm; a relatively short inclined arm member on the end of saidlever remote from said housing; a knife edge bearing member on the outerend of said rod engaging said short arm member adjacent the junction ofthe same with said lever arm; and means rigid with the outer end portionof said tube engaging the end of said short lever arm, said rod and saidtube having unequal coelcients of expansion whereby said lever arm maybe moved by reaction of said rod and said tube in response to changes oftemperature.

6. In thermostatic apparatus, a tube having one end closed and adaptedto be immersed in fluid of variable temperature; a housing rigidlysecured to the other end of said tube; a shoulder provided in saidhousing adjacent the end of said tube; a rod member disposedlongitudinally within said tube and extending into said housing, saidrod member having a different coeiiicient of expansion than said tube; aremovable end plate on said housing; a tubular boss on the inner side ofsaid end plate receiving the end of said rod; guide slots extendinglengthwise of said boss; a cross pin in said rod guided in said guideslots; an adjusting screw threaded into said tubular boss providing athrust support for the end of said rod; a pointer member on the outerend of said adjusting screw; a movable lever member extending lengthwisein said tube and positioned above said rod; a relatively short rigidinclined arm on the outer end of said lever member; a knife edge bearingmember on the outer end of said rod engaging said short arm adjacent thejunction of the same with said lever member; means rigid with the closedouter end portion of said tube engaging the end of said short lever arm,whereby said lever arm will be angularly moved in response todifferences in the relative lengths of said rod and said tube producedby changes of temperature; a switch lever positioned in said housing inapproximate alignment with said lever arm, said switch lever havingspaced apart arms fulcrumed on said shoulder of said housing adjacentthe end of said tube; a tension spring positioned between said spacedapart arms of said switch lever and connecting said switch lever with-said lever arm; and circuit opening and closing means carried by saidswitch arm.

DIRK EISINGA.

